Borrelia burgdorferi in tick cell culture modulates expression of outer surface proteins A and C in response to temperature

The Lyme disease spirochete Borrelia burgdorferi sensu stricto downregulate s outer surface protein A (OspA) and upregulates outer surface protein C (O spC) during tick feeding. The snitching of these proteins correlates with i ncreased spirochetal infectivity for the mammal. We examined the effect of temperature on differential expression of OspA and OspC by B. burgdorferi c ocultivated with a cell line isolated from the vector tick Ixodes scapulari s. The effect of incubation at 31, 34, or 37 degrees C on expression of Osp A and OspC by B, burgdorferi JMNT and N40 was analyzed by indirect fluoresc ent-antibody microscopy! polyacrylamide gel electrophoresis, and immunoblot ting, The amount of OspA relative to the amount of flagellin was highest in spirochetes cocultivated with tick cells at 31 degrees C and declined with increasing temperature in both strains. OspC production was enhanced in sp irochetes cocultivated with tick cells at 37 degrees C. Spirochetes grown a xenically in BSK-H medium also produced more OspC at 37 degrees C, but OspA content was not appreciably affected by temperature. Our findings indicate that temperature, along with cultivation in a tick cell culture system, pl ays a role in the differential expression of OspA and enhances differential expression of OspC by spirochetes.